1. Field of the Invention
This invention relates to a process for preparing novel polymeric flame retardant additives, the resulting polymeric flame retardant additives themselves, and non-burning fibers or films containing these flame retardant additives.
2. Summary of the Prior Art
As in well known, cellulose acetate and cellulose triacetate enjoy widespread commercial acceptance for the production of oriented shaped articles such as fibers or films. However, these acetates are flammable, i.e., they not only burn upon application of a flame, but they lack self-extinguishing characteristics. This flammability propensity renders these acetates unsuitable for the production of fibers and films intended for utilization in fire-critical areas, e.g., such end-uses as children's clothing and sleepwear, and carpets, sheets, and draperies in hospitals, nursing homes, etc.
Although the prior art contains some examples of non-burning cellulose acetate and cellulose triacetate compositions, many are not commercially acceptable. For example, it is known to use non-polymeric flame retardant compounds such as tris(2,3-dibromopropyl)phosphate, bis(2-chloroethyl)-2-chloroethylphosphonate, octabromobiphenyl, and hexabromobenzene either alone or in combination with other flame retardant additives to make materials such as fibers and films less flammable. However, the use of such non-polymeric flame retardant compounds in fibers and films may be disadvantageous in that the relatively small size of the non-polymeric molecules makes them susceptible to removal from the fibers or films. For example, exudation of these non-polymeric additives may occur--especially at elevated temperatures. The additive may become visually apparent upon the surface of the fibers or film as a fine powder. Also, non-polymeric flame retardant additives may be removed from the fibers or film by washing or dry cleaning.
It is also known to use polymeric compounds as flame retardant additives for certain film forming materials. For example, U.S. Pat. No. 2,636,876 discloses phosphorus and chlorine containing polymers which have a flame-retardant effect on nitrocellulose.
The search has continued for improved polymeric additives which possess flame retardant characteristics and which are non-exuding from cellulose acetate and cellulose triacetate fibers and films.